The present invention relates to an electrode wire for wire electric discharge machining.
More particularly, the present invention relates to an electrode wire for wire electric discharge machining which allows a workpiece to be melted and cut at high speed when causing an electric discharge to occur between the wire and the workpiece, exhibits higher productivity in comparison with a conventional high-speed electrode wire, and has excellent recyclability.
Wire electric discharge machining is a machining method which causes a workpiece to be melted and cut by causing an electric discharge phenomenon to occur between an electrode wire for wire electric discharge machining and the workpiece.
Since this machining method enables machining such as that using a fretsaw, this machining method is particularly suitable for machining a complicated shape.
As the electrode wire for wire electric discharge machining, an electrode wire is desired which enables high-speed machining and is inexpensive so that electric discharge machining cost can be reduced.
From the viewpoint of convenience, an electrode wire which enables an automatic connection so as to be able to deal with automated machining, or an electrode wire which rarely breaks is also desired.
An electrode wire made of a binary alloy of copper and zinc with a zinc content of 35 to 40% has been widely and generally used as such an electrode wire.
An electrode wire made of a binary alloy of copper and zinc with a zinc content of 35 to 40% is comparatively inexpensive, but is not necessarily sufficient from the viewpoint of the machining speed and the characteristics when causing a workpiece to be melted and cut.
Therefore, an electrode wire having a two-layer structure as shown in FIG. 4, in which a high-zinc-content brass layer is provided outside a core copper alloy in order to improve discharging properties, has been commercialized as an electrode wire in pursuit of high-speed machinability, for example.
An electrode wire having a three-layer structure as shown in FIG. 5, in which zinc is further provided in the outermost layer in order to further increase the speed, is also known.
The electric discharge machining speed is increased by increasing the zinc content in the coating layer. However, since the electrode wire having a multilayer structure has a complicated structure, manufacturing cost of the electrode wire is increased to a large extent.
Japanese Patent No. 3303296 discloses a technology aiming at increasing the zinc content while using a simple single-layer structure.
However, wire drawing cannot be substantially performed without adding an additional element such as Zr, Al, or Si, as described in the section “Means for Solving the Problems and Effect of the Invention” in this patent document which states “the electric discharge machining characteristics are improved by increasing the zinc content. However, processing into a thin wire is difficult by using a conventional processing method due to occurrence of the β phase”.
However, the addition of such an additional element not only increases cost, but also poses a recyclability problem from the viewpoint of electrode wire wastes.